File 0002-btrfs-progs-Ignore-devices-representing-pa... of Package btrfsprogs.23274

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File 0002-btrfs-progs-Ignore-devices-representing-paths-in-mul.patch of Package btrfsprogs.23274

From 981fa4b55ded238624faa683fd7a6f6bc01f1f95 Mon Sep 17 00:00:00 2001
From: Nikolay Borisov <nborisov@suse.com>
Date: Thu, 30 Sep 2021 15:06:33 +0300
Subject: [PATCH 2/3] btrfs-progs: Ignore devices representing paths in
 multipath

Currently btrfs-progs will happily enumerate any device which has a
btrfs filesystem on it irrespective of its type. For the majority of
use cases that's fine and there haven't been any problems with that.
However, there was a recent report that in multipath scenario when
running "btrfs fi show" after a path flap (path going down and then
coming back up) instead of the multipath device being show the device
which represents the flapped path is shown. So a multipath filesystem
might look like:

Label: none  uuid: d3c1261f-18be-4015-9fef-6b35759dfdba
        Total devices 1 FS bytes used 192.00KiB
        devid    1 size 10.00GiB used 536.00MiB path /dev/mapper/3600140501cc1f49e5364f0093869c763

/dev/mapper/xxx is actually backed by an arbitrary number of paths,
which in turn are presented to the system as ordinary scsi devices i.e
/dev/sdX. If a path flaps and a user re-runs 'btrfs fi show' the output
would look like:

Label: none  uuid: d3c1261f-18be-4015-9fef-6b35759dfdba
        Total devices 1 FS bytes used 192.00KiB
        devid    1 size 10.00GiB used 536.00MiB path /dev/sdd

This only occurs on unmounted filesystems as those are enumerated by
btrfs-progs, for mounted filesystem the kernel properly deals only with
the actual multipath device.

Turns out the output of this command is consumed by libraries and the
presence of a path device rather than the actual multipath causes
issues.

Fix this by checking for the presence of DM_MULTIPATH_DEVICE_PATH
udev attribute as multipath path devices are tagged with this attribute
by the multipath udev scripts.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 utils.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/utils.c b/utils.c
index 3a4bc92a66ac..710c566a0548 100644
--- a/utils.c
+++ b/utils.c
@@ -17,6 +17,10 @@
  * Boston, MA 021110-1307, USA.
  */
 
+#ifdef STATIC_BUILD
+#undef HAVE_LIBUDEV
+#endif
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -39,6 +43,9 @@
 #include <sys/statfs.h>
 #include <linux/magic.h>
 #include <getopt.h>
+#ifdef HAVE_LIBUDEV
+#include <libudev.h>
+#endif
 
 #include <btrfsutil.h>
 
@@ -1966,6 +1973,43 @@ int group_profile_max_safe_loss(u64 flags)
 	}
 }
 
+#ifdef HAVE_LIBUDEV
+static bool is_path_device(char *device_path)
+{
+	struct udev *udev = NULL;
+	struct udev_device *dev = NULL;
+	struct stat dev_stat;
+	const char *val;
+	bool ret = false;
+
+	if (stat(device_path, &dev_stat) < 0)
+		return false;
+
+	udev = udev_new();
+	if (!udev)
+		goto out;
+
+	dev = udev_device_new_from_devnum(udev, 'b', dev_stat.st_rdev);
+	if (!dev)
+		goto out;
+
+	val = udev_device_get_property_value(dev, "DM_MULTIPATH_DEVICE_PATH");
+	if (val && atoi(val) > 0)
+		ret = true;
+out:
+	udev_device_unref(dev);
+	udev_unref(udev);
+
+	return ret;
+}
+#else
+static bool is_path_device(char *device_path)
+{
+	return false;
+}
+#endif
+
+
 int btrfs_scan_devices(void)
 {
 	int fd = -1;
@@ -1994,6 +2038,9 @@ int btrfs_scan_devices(void)
 		/* if we are here its definitely a btrfs disk*/
 		strncpy_null(path, blkid_dev_devname(dev));
 
+		if (is_path_device(path))
+			continue;
+
 		fd = open(path, O_RDONLY);
 		if (fd < 0) {
 			error("cannot open %s: %m", path);
-- 
2.25.1

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